Cutworms

Cutworms have continued to cause problems, although the worst may now be behind us. Looking to the future, some predictions can be made.

 

Where have they been reported?

Cutworms have continued to cause problems, although in most regions the worst is now likely to be behind us. In the Donald area of the Victorian Wimmera, some estimates indicate half of all cereal crops have been sprayed for cutworms. Alpha-cypermethrin, applied at label rates, has been effective but can be slow to work particularly on larger caterpillars. In paddocks north of Nhill, also in the Wimmera, a second wave of younger cutworm caterpillars (about 10 mm) have been reported damaging wheat and canola. The damage is variable, and sprays have not yet been required.

In the Victorian Mallee, cutworms have also been problematic; in some regions this has only occurred in the last few weeks. This is surprising given they first appeared more than 4-8 weeks earlier in the Victorian Wimmera and parts of the NSW Riverina. Around Manangatang, 10-30 mm caterpillars have been observed in many paddocks, attacking plant stems and occasionally leaves.

Near Walla Walla, in the NSW Riverina, the damage caused by cutworm infestations in canola and cereals continues to amaze growers. Most paddocks have been sprayed to control caterpillars. In the Lockhart and Conargo areas (also in the NSW Riverina) cutworm densities and crop loss have also been extreme, particularly in young canola crops. At Ariah Park, in the NSW Central West, cutworms have reportedly reached densities of up to 50 per square metre, while reports indicate cutworm damage in crops north of Grenfell, in the NSW Central Tablelands, is now beginning to subside.

Refer to PestFacts Issue No. 4 for further information on cutworms. 

Our advice

Cutworm reports will continue to diminish now the cooler weather has arrived, many paddocks have been sprayed and most crops have become established. We recommend care is taken to monitor and accurately identify caterpillars found to be causing damage. If cutworms are confirmed and spraying is warranted, there is little to be gained from increasing insecticide rates beyond those registered.  Growers are understandably concerned about re-invasion of cutworms later in the year and again in 2015. Below we speculate about cutworm infestations over the next 3-12 months:

- Cutworms are likely to cease eating and pupate in June, July and August, depending on their current stage of development.

- Once a crop is established, cutworms are unlikely to cause serious defoliation as they are less inclined to climb plants like armyworms and native budworm.

- Most cutworm moths will emerge in spring and migrate. We do not expect major problems with cutworms in spring-planted crops.

- The scale of infestations experienced this season is unlikely to be repeated in 2015. This is because the natural enemies of ‘plague pests’ like cutworms are often out-of-synchrony with the pest. Natural enemies (many wasp, fly and beetle species) will be building up this year, along with many insect disease pathogens; these are likely to impact heavily on the next generations of cutworms.

 

* Sources of field reports of cutworms

Lachlan Caldwell – Agronomist, H.O. Rider & Sons (NSW Central Tablelands)

Terry Edis – Agronomist, Landmark (NSW Central West Slopes & Plains)

David Eksteen – Agricultural Consulting (NSW Riverina)

Rik Maatman – Agronomist, Landmark (Victorian Wimmera)

Andrew McMahen – Agronomist, Landmark (Victorian Mallee)

Adam Pearce – Agronomist, Clovercrest Consulting (Victorian Wimmera)

Damien Tanner – Agronomist, JSA Agronomy (Victorian Wimmera)